1. Field of the Invention
The present invention relates to the field of handling sheet-like product assortments, as is performed, for example, in the further processing of printed products. It relates to a method for applying at least one enclosing element to a sheet-like product assortment as claimed in the preamble to claim 1. It also relates to an enclosing element application device for performing the method.
2. Discussion of Related Art
Today there is an increasing quantity of advertising material, in the form of sheet-like upstream products, such as brochures, flyers, catalogs, leaflets, mail circulars but also product samples, CDs, etc., that is distributed directly by specialized service providers. Advertising material from different providers are here often combined and distributed together in order to keep distribution costs low. The advertising material or upstream products that are distributed together then form a stack of individual copies lying one on top of the other which then needs to be assorted by hand, for example, by the distributor in each case at the point of supply. However, this manner of assortment is time-consuming and liable to error so that certain pieces of advertising material may either appear several times in the stacks that have been formed or be missing altogether.
Stacks are here understood in principle to be assortments of sheet-like upstream products that lie one on top of the other and are held together by gravity. If the upstream products are aligned in a different spatial orientation, for example vertically with one lying on top of the other, they are here also referred to as a collection. The invention relates essentially to such different manners of assorting the upstream products, which will be referred to below as product assortments.
When stack-like product assortments or sheet-like products are processed, as occurs for example when printing newspapers, it is often desirable to hold such product assortments together by applying strips, or to differentiate them from other product assortments.
If a large number of product assortments need to be processed per unit time, i.e. need to be provided with such strips, in this way, the corresponding method needs to be simple to perform, allow a high processing speed, and moreover be able to operate in an operationally reliable manner.
A method and a device for producing multi-part units of printed products are known from EP 0 666 186 A1, in which inserts are arranged inside a folded newspaper that serves as the outer part of the product unit. A piece of adhesive tape joins the two halves of the newspaper together in order to stop the inserts from slipping and prevent them from falling out of the newspaper. The pieces of adhesive tape are here cut off from an adhesive tape before being applied and the individual pieces are then transported and deposited by means of a separate transportation apparatus to the newspapers that are situated in a drum with pocket-like holding parts and are moved on a circular track. This manner of application requires highly complex machinery.
U.S. Pat. No. 5,096,176 and EP 0 493 109 A1 describe a device and a method by means of which one edge of a stack of sheets of paper is provided with a non-adhesive paper strip in such a way that multiple stacks are reliably separated from each other. To do this, a strip of paper is fed from a roller so that it crosses into the transportation path of the stack, so that the transported stack carries along the strip of paper and at the same time leads it past a downstream blade in such a way that a piece of strip is cut off from the strip of paper. The stack with the cut-off piece of strip is then guided between two belts that are circulating in parallel, wherein the piece of strip is folded around the front edge of the stack. Owing to the distance between the position of the crosswise strip and the downstream belts, it is not possible to apply pieces of adhesive tape and this should be expressly avoided.
DE 69214614 T2 discloses a method and a device for temporarily joining together multiple sheets of an information recording medium. To do this, segments of adhesive joining tape are provided at opposite ends and are applied around the edge of a compiled set stack by means of a displaceable application means. Complicated, mechanically movable machinery is used for cutting and applying the segments which has a complex structure, is slow when in use, and is prone to operational faults owing to its complexity.
A method for wrapping a stack of sheets, brochures or the like is known from WO 2008/074325 A1 in which the stacks are transported, spaced apart, one behind the other on a transportation path. A wrapping sheet is drawn off by means of a specialized swivel wheel from a sheet supply that is held ready for use, is positioned vertically in a gap between two successive stacks, and is then folded around the stack that is moved past by means of the swivel wheel. The complicated movement of the swivel wheel militates against a high stack processing speed.
EP 1 409 347 B1 discloses a method for enveloping printed matter by arranging a film around the printed matter. The film is here arranged on a first conveying device. The printed matter is then arranged partially on top of the film so that a part of the film that is at the front in the direction in which it is conveyed is not covered by the printed matter. A rising stream of air is then provided, as a result of which the front part of the film is blown upward into a vertical position. The printed matter with the film is then conveyed onward beneath an upper strap, as a result of which the film is folded back along the top of the printed matter. The problem here is that the film must first be laid on the transportation mechanism and positioned there, and the printed matter must then correspondingly be deposited on the film and similarly positioned. This requires complex machinery and restricts the processing speed.
U.S. Pat. No. 6,464,819 describes a method and a device for sealing folded material that has a folded end and an open end and is intended to be sealed at the open end so that it can be mailed. The method is thus similar to sealing an open envelope that has already been joined together at the folded end. Product assortments within the sense of the present application, in which sheet-like products lie loosely on top of one another, are not the subject of this document.
U.S. Pat. No. 3,507,089 A relates to a bundling device in which multiple cigarette packets arranged next to one another and on top of one another are combined in a complicated method to form a stick and are completely enclosed and packaged with a wrapping material. The packaging material is thus supplied as a broad web perpendicular to the transportation path, a piece is cut off by a rotating blade and the piece is carried along by the stick.
A similar device for completely wrapping stacks of paper sheets is known from U.S. Pat. No. 3,996,728.